1. Field of the Invention
The present invention relates to a disc cartridge having a flat restraint which forces a disc downwardly so that the disc cannot move in the disc cartridge body when it is not in use.
2. Description of the Prior Art
A disc cartridge, in which a disc is forced toward the lower shell of a cartridge body by means of a disc restraint so as not to move in the cartridge body when it is not in use and, when the disc cartridge is loaded on a disc drive unit, the restraint is released from engagement with the disc by means of a release pin is the subject of U.S. Pat. application Ser. No. 217,439 filed July 11, 1988. Referring to FIGS. 3 to 6, this disc cartridge is described in detail. Reference number 1 refers generally to a disc cartridge. A cartridge body 2 of the disc cartridge 1 comprises an essentially square upper shell 3 made of a synthetic resin and a matching lower shell 4, also made of a synthetic resin, the periphery of which is joined to the periphery of the upper shell 3. A magnetic disc 5 is rotatably housed in a space formed between the inner surface 3a of the upper shell 3 and the inner surface 4a of the lower shell 4.
A rectangular recess 3b is formed on the inner surface 3a of the upper shell 3 at an essentially central location. A tapered surface 6 is formed in the recess 3b. A long, rectangular head-receiving opening 7a serving as a disc-exposing opening is formed in the upper shell 3.
In order to insert a turntable 30 of a disc drive unit (not shown), a center opening 8 is formed on the bottom of the lower shell 4 at the center. A long and narrow receiving opening 9 is formed in the lower shell 4 at the left, lower corner portion as viewed in FIG. 3. In addition, a head receiving opening 7b, the shape of which is the same as that of the head receiving opening 7a, is formed in the bottom of the lower shell 4 at a location corresponding to the head receiving opening 7a of the upper shell 3. These head receiving openings 7a, 7b may be opened and closed by menas of a slidable, U-shaped shutter 10. The shutter 10 is biased by means of an esentially V-shaped spring 11 so as to always close the head receiving openings 7a, 7b, so that dust or the like cannot be introduced into the interior of the cartridge body 2 through the head receiving openings 7a, 7b when the disc cartridge is not in use. Furthermore, reference openings 12 and 13 are formed on the bottom of the lower shell 4 at the left and right lower corners, respectively.
The magnetic disc 5 is a thick disc made of a polyetherimide (PEI) or the like. Recording and reproducing can be performed on both surfaces thereof by means of a magnetic head or othe like of the disc drive unit. A ring-shaped hub 14 made of a synthetic resin is inserted into a hub receiving opening 51, which is formed in the magnetic disc 5 at the center thereof, to be fixed to the magnetic disc 5 by means of screws 15, adhesive or the like. Three flat springs 16 are provided on the inner periphery of a center opening 14a of the hub 14 so as to form an essentially equilateral triangle. A shaft 30a a of the turntablel 30 is inserted between these three flat springs 16. In addition, a ring-shaped metallic plate 17 is fixed to the lower surface of the hub. The metallic plate 17 adheres to a disc-shaped magnet 32 fixed to the upper surface of the turntable 30 when the disc cartridge 1 is loaded on the turntable 30.
The upper surface 14b of the hub 14 may be engaged by or released from engagement with a restraint 18. The restraint 18 comprises an essentially F-shaped metallic plate. Ends 18a, 18b of the restraint 18 are slidable on a ring-shaped rib 4b which is provided on the inner surface 4a of the bottom of the lower shell 4. The tip of a center portion 18c of the restraint 18 is formed to be an E-shaped, the center portion of which is bent at a predetermined angle and provided with a tapered portion 19 which comes into contact with the tapered surface 6 of the upper shell 3. In addition, the lower end of the left-hand end portion 18a of the restraint 18 in FIG. 3 is rectangularly bent to form an engagement portion 20 which engages a release pin 31 inserted into the receiving opening 9 of the lower shell 4. The engagement portion 20 is integrally formed with a flat compression spring 21 serving as a biasing member for the restraint 18. The flat compression spring 21 is bent to be essentially U-shaped, the tip 21a of which is in contact with the peripheral wall 4c of the lower shell 4 so as to bias the restraint 18 toward the shutter 10.
As shown in FIG. 4, when the disc cartridge 1 is not in use, the restraint 18 is moved downwardly toward the disc 5 by the elastic force of the flat compression spring 21 of the restraint 18 and by contact between the tapered surface 6 of the upper shell 3 and the tapered portion 19, so that the hub 14 is forced downwardly by means of the center portion 18c of the restraint 18, whereby the lower surface of the magnetic disc 5 on the side of the hub receiving opening 5a is forced against the ring-shaped rib 4d of the lower shell 4 on the side of the center opening 8. As a result, the magnetic disc 5 is prevented from moving within the cartridge body 2.
When the cartridge body 2 is loade do nthe turntablel 30 of the disc drive unit, the release pin 31 of the disc drive unit engages the engagement portion 20 of the restraint 18 as shown in FIG. 6. From this state, the release pin 31 is moved in the direction of the aarrow in FIG. 6 against the elastic force of the flat compression spring 21 of the restraint 18 by means of a release pin driving mechanism (not shown). As a result, as shown in FIG. 5, the center portion 18c of the restraint 18 is moved upwardly into the recess 3b of the upper shell 3 and released from the upper surface 14b of the hub 14, so hat the force of the restraint 18 against the magnetic disc 5 is released and the hub 14 is engaged by the magnet 32 of the turntable 30.
However, since the opening 9 for receiving the release pin 31 is open, dust or the like can be introduced into the cartridge body 2.
It is, therefore, an object of the present invention to provide a disc cartridge 1 in which dust or the like cannot be introduced into the cartridge body 2 through the long and narrow receiving opening 9 receiving the release pin 31.